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Concrete vs steel columns for elevated deck

pacificstart's picture

I am trying to figure out the easiest way to build the columns for balcony from the attached picture. In the picture the columns are shown with brick finish but they be finsidhed with stucco in order to match and blend im with the balcony walls. 

This design will be reviewed and stamped by and engineer but the execution will be a DIY project.

I have never done anything similar before so any comments are appreciated.

The balcony area is about 32x6 ft and 9ft high. The colums are cca 12"x12" wide. The balcony deck structure will be done with light gauge steel framing.

The project requires to use either poured concrete pillars or steel columns which will be covered with EPS foam and stuccoed.

I am inclined to use steel columns rather than concrete because the project is on slope and the heavy weight of the concrete posts may lead to non-uniform settling over time.

The steel columns will need to be sunk about 4ft in a concrete base and height of the brackets attaching to the deck will have to be adjustable to for varaiation in height during installation or settling.

Here is the order of operations I envision:

1

Dig holes for the columns concrete base

2

Place steel columns in holes together with required rebard around, etc.

3

Adjust column height and alignment. Leave 1/2" room for shimming at the top of the columns for future height adjustment.

4

Brace and support columns with 2x lumber.

5

Build deck structure and attach it to the house and columns.

6

Pour concrete base and verify height and alignment of columns before curing of concrete.

7

Perform final height adjustments/shimming and finalize all the deck attchements.

8

Attach railings/parapet walls and finish the surfaces are required.

 

Does this sound ok? Did I miss anything or do you see any operation that requires special attention?

 

TIA

Steven

By all means steel. (post #215897, reply #1 of 8)

Pouring a concrete column of that height is not a job for the faint of heart. There's too much that could go wrong. 

If your footing design is good there should be minimal settling. If your engineer calls for the columns to be sunk in concrete then so be it, but it would be much easier to sink anchor bolts and then put the columns after the concrete has been done. This is done all the time. I certainly would not build the deck structure before the concrete. There's no good reason why the columns can't be accurately placed and supported before the concrete. You can't put the colums directly into the ground. They need to have concrete under them. How much is up to your engineer. That doesn't mean you can't place them and then pour around them, you just are going to have to leave room for concrete underneath. This could be a footing of considerable size, so you may need to use sono tubes around the columns if you have to embed them. 

I'd build a temporary A frame structure, suspend the columns and then brace them plumb, but again ask your engineer about bolts. 

Thank you (post #215897, reply #7 of 8)

mike mahan wrote:

Pouring a concrete column of that height is not a job for the faint of heart. There's too much that could go wrong. 

If your footing design is good there should be minimal settling. If your engineer calls for the columns to be sunk in concrete then so be it, but it would be much easier to sink anchor bolts and then put the columns after the concrete has been done. This is done all the time. I certainly would not build the deck structure before the concrete. There's no good reason why the columns can't be accurately placed and supported before the concrete. You can't put the colums directly into the ground. They need to have concrete under them. How much is up to your engineer. That doesn't mean you can't place them and then pour around them, you just are going to have to leave room for concrete underneath. This could be a footing of considerable size, so you may need to use sono tubes around the columns if you have to embed them. 

I'd build a temporary A frame structure, suspend the columns and then brace them plumb, but again ask your engineer about bolts. 

mike mahan wrote:

Pouring a concrete column of that height is not a job for the faint of heart. There's too much that could go wrong. 

If your footing design is good there should be minimal settling. If your engineer calls for the columns to be sunk in concrete then so be it, but it would be much easier to sink anchor bolts and then put the columns after the concrete has been done. This is done all the time. I certainly would not build the deck structure before the concrete. There's no good reason why the columns can't be accurately placed and supported before the concrete. You can't put the colums directly into the ground. They need to have concrete under them. How much is up to your engineer. That doesn't mean you can't place them and then pour around them, you just are going to have to leave room for concrete underneath. This could be a footing of considerable size, so you may need to use sono tubes around the columns if you have to embed them. 

I'd build a temporary A frame structure, suspend the columns and then brace them plumb, but again ask your engineer about bolts. 

Thank you - now it makes sense.

When I started planning for this - like three years ago or so I had no idea about current construction technique.

After three years of researching and talking to people at least I now have an idea and this kind  information helps me ask pertinent questions to the trades and such.

conc. vs stl (post #215897, reply #2 of 8)

In all due respect, it seems to me that you are going about this backwards.  You need to start discussing  with the engineer what your problem is and then you and he come up with a solution.

Start out with professional knowledge and not with DIY ideas.  Obviously, I'm not there, but what you have posted seems that you don't have a real handle on how to do the job. Sorry if I have offended,  but you ask.

"pacific' in your post (post #215897, reply #3 of 8)

"pacific' in your post implies sesmic area.

Hence, no brainer, steel.  

 

plus appropriate sesmic calculations,  1.4g horizontal, 1`.2g vertical if in cascada subduction zone, only about 1 g on san andreas or oter faults.  (of the top of head IIRC number, look up USGS data sheets for correct design number. 

Cascadia it is (post #215897, reply #6 of 8)

junkhound wrote:

"pacific' in your post implies sesmic area.

Hence, no brainer, steel.  

 

plus appropriate sesmic calculations,  1.4g horizontal, 1`.2g vertical if in cascada subduction zone, only about 1 g on san andreas or oter faults.  (of the top of head IIRC number, look up USGS data sheets for correct design number. 

junkhound wrote:

"pacific' in your post implies sesmic area.

Hence, no brainer, steel.  

 

plus appropriate sesmic calculations,  1.4g horizontal, 1`.2g vertical if in cascada subduction zone, only about 1 g on san andreas or oter faults.  (of the top of head IIRC number, look up USGS data sheets for correct design number. 

Junkhood - good observation!

cascadia is about 100 miles from here. Thanks.

CMU? (post #215897, reply #8 of 8)

I worked with my engineer on design for a freestanding deck coming off the main floor that was 10 feet above ground at the house and 15 feet off the ground 12 feet out (a good slope). We built significant footings for columns that supported steel I-beams (w8/21 galvanized).  We had soil test to figure out where undisturbed soil was and engineer told me in each place how far down to dig. He spec'd about 6' deep holes 32x32 (I made them 36" square) and gave me the rebar design. I needed to have 18" thick footings, but he let me just fill the hole up with concrete. The cost for that was a few hundred dollars and that sounded easier than laying block into a 4' deep hole. Four rebar came up from the footing into the CMU cavity and mason laid the block up for each column (16x16). We then had concrete pump back out to put in block fill making a solid column, but "formed" by the CMU. All told it was very efficient and rock solid base of 7 columns for a 12' x 36' deck. The key is to have a great pump operator and experienced crew when you do that block fill. Standing on a ladder with a 2" hose has some inherent risks and the pump operator was not great (machine settings were wrong, was getting surges and too high of pressure; fortunately the driver of the (volumetric) truck (pump and supplier were the same company) was experienced in pumping and placing concrete and he took over the hose and told the pump operator to turn the pump pressure down. I gave that guy a big tip. Just another option for how to get to a stable base for the deck. Once the beams were in place, the deck got built pretty straighforwardly with pt joists set on the beams (which had a top plate bolted on per engineer's bolt schedule).